Dave Jones

that calc looks wrong. its the uncorrected U value by the looks. try https://www.changeplan.co.uk/

if your build is 3 month stasrt to finish timber frame is worth the premium if not your wasting the double cost of a timber frame over a standard build. that wasted cash can buy a lot of 2nd fix items.

link to the blocks with 0.09 U ? aerated conc are crap for air tightness and the normal ones are 0.15U still a fail for regs.

you need to lift a lid and see what size pipe it is. Highly unlikely you will be allowed to build over. They would insist on a divert if thats even possible. £££££££££££££££££££££££££ be very very careful

without question fancoil units in bedrooms. primarily for cooling. wouldnt be without them having experienced last summer.

sure about that ?

Is it bare soil or stoned already ? DPM membrane ? normal practice is 100mm hardcore whacked, sand blinded, DPM lapped up to house DPC, insulation min 150, screed 75mm

you have a QS price the foundations same as all the other build elements. The bank will use this to pay you. Zero chance for ambiguity then!

use a building warrant and avoid having to pay for any paperwork. dead cash. Just provide the normal certs on completion for signoff.

you dont need sign offs to get paid. When the QS visits, he will check the progress on elements. for example if the walls are half done you can claim half the QS cost. 3 out of 5 windows in same etc etc They wont pay for any materials on site that are not built in. Found them very reasonable. Go through your QS and mark it up showing % completion of the elements and email it them before the visit.

150 cav is much easier to source batts for and is also the minimum cavity to meet new build spec when using batts. just because your extension doesnt have to meet new build regs, i'd still not want a poorer standard. no need for any internal insulation then.

good luck ever getting close to having a builder complete that. You need a rocket scientist ! You have 6 different types of membranes in that 'detail' Have to keep it much simpler to stand a chance of getting it done correctly.

got it so steeper means less yield ? Could allways hang a bunch on some fencing ?

dont be silly. its a bodge, marmox are designed to eliminate this cold bridge. Nothing stopping using blocks as every house has done for years it will save a few pennies but its wrong and is still a cold bridge.